More than 171,000 people across 22 provinces were directly affected by Nesat on 27 September, the 16th cyclone to have hit the archipelago nation this year and considered one of the strongest, with a 650km radius rain band.
According to the National Disaster Risk Reduction and Management Council (NDRRMC) on 28 September, many areas of Luzon Island, the country's most populated area, remained without power and cut off from emergency services by landslides, floods and debris that littered many highways.
More than 47,000 families remained in 153 evacuation camps, mostly sports stadiums and schools whose sanitation facilities are not equipped to handle a large influx of people.
NDRRMC executive director Benito Ramos told IRIN that cramped centres in the Manila Bay slum neighbourhoods, evacuated after storm surges, could be among the areas severely affected by disease.
"In coordination with the Health Department, we have deployed emergency management service personnel to supervise sanitation and other issues, including drinking water and distribution of medicines," Ramos said.
He said small children were especially vulnerable to common colds or diarrhoea, while Leptospirosis - a bacterial infection that causes high fever and jaundice and is commonly spread by rats through urine - was a cause for concern because many areas remained submerged.
"We are trying our best to help everyone and ensure that diseases are checked," he said.
Philippine National Red Cross Secretary-General Gwen Pang said health volunteers had fanned out to promote sanitation education as well as help affected medical institutions cope with the disaster.
It said one hospital, the Ospital ng Maynila near the bay, had to relocate some patients after flood waters partly submerged it, temporarily shutting down its emergency ward. It has, however, resumed operations, though a massive clean-up is still under way.
"Trained social workers are providing counselling and psycho-social support. And in terms of preventing spread of diseases, we are doing a rapid assessment and promoting vaccinations and distributing hygiene kits," Pang said.
"We are also distributing water purifiers and medicines. We also have first aiders for those who suffered injuries."
Nesat barrelled its way across Luzon from the Pacific Ocean on 27 September, bringing torrential rains and unprecedented storm surges that breached Manila's seawall.
Saltwater flooded a main boulevard, a hotel and the US embassy, while elsewhere authorities were forced to release water from dams that inundated villages in Luzon's Bulacan Province.
The typhoon also toppled power lines and uprooted trees, rendering nearly two million people without electricity for 24 hours, including in Manila, where the health department said some hospitals struggled with petrol-run generators.
But the civil defence office in Manila said logistical support was under way, with local governments helping to access pre-positioned medical supplies, Ramos said.
According to the UN Office for the Coordination of Humanitarian Affairs, the Philippines government is leading response efforts and has not requested international assistance.
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